An energy storage system (ESS), an electric vehicle (EV), and the like, which use a high-voltage battery pack, are equipped with a system that automatically interrupts power when an emergency situation occurs. The “emergency situation” refers to an excessive short circuit, insulation breakdown, etc., which are caused by aging of an associated component, and an excessive short circuit, insulation breakage, etc., which are caused by a short circuit caused by component breakage due to an external impact.
When an emergency situation occurs, a command for interrupting main power is transmitted from a higher-order component for controlling high-voltage components such as a battery management system (BMS) or a hybrid control unit (HCU), thereby controlling the power. The high-voltage associated component monitors voltage and current of a line connecting the power through a series of programs or sensors, and interrupts the main power through CAN communication or signal transmission when voltage and current, which are out of a normal range, are detected or there occurs leakage current, which is equal to or higher than an allowable value, and when there occurs insulation resistance breakage, which is equal or higher than the allowable value.
As described above, it is very important to measure insulation resistance in the ESS, the EV, and the like using the high-voltage battery pack. Examples of a method for measuring the leakage current of the battery pack include a method of forcing direct current (DC) to flow by breaking insulation, and such a method has a disadvantage in that the insulation is broken while the insulation resistance is measured.
There is a method of measuring an insulation resistance component by connecting a capacitor to a battery pack and applying an AC signal to the capacitor in order to solve the disadvantage. However, the method also has a disadvantage in that since current charging the capacitor and discharged current need to pass through the same circuit, there are a lot of limits in designing the circuit.
Further, when a voltage measurement time for measuring the insulation resistance is delayed due to a delay of voltage falling and rising by a capacitor component, such that the insulation breakage occurs, there is a problem in that the insulation breakage cannot be rapidly detected.
Therefore, in order to solve the aforementioned problem, the present inventors have invented an insulation resistance measuring system and device, which determine whether first voltage of a first measurement resistance connected with a positive electrode insulation resistance in parallel and second voltages of second measurement resistances connected with a negative electrode insulation resistance in parallel converge, respectively, control connection of the positive electrode insulation resistance and the negative electrode insulation resistance and the first and second measurement resistances according to whether the first and second voltages converge, respectively, and calculate resistance values of the positive electrode insulation resistance and the negative electrode insulation resistance by using convergence values of the first and second voltages.